WO2017215560A1

WO2017215560A1 - Fingerprint sensor and electronic device

Info

Publication number: WO2017215560A1
Application number: PCT/CN2017/087917
Authority: WO
Inventors: 王小明
Original assignee: 深圳信炜科技有限公司
Priority date: 2016-06-13
Filing date: 2017-06-12
Publication date: 2017-12-21
Also published as: CN106778462B; CN106778462A

Abstract

A fingerprint sensor and an electronic device. The fingerprint sensor (100) comprises a plurality of sensing electrodes (102), a protective layer (104) and a plurality of operational amplifiers (106). The protective layer (104) is on the same layer as the plurality of sensing electrodes (102), the protective layer (104) is arranged around each sensing electrode (102), the protective layer (104) is connected to a reference ground (200), and the reference ground (200) is used for loading a varying reference signal. Each operational amplifier (106) comprises an amplifier (108) and a feedback branch (110); and the amplifier (108) comprises a non-inverting end (V+), an inverting end (V-) and an output end (V0), wherein the inverting end (V-) is connected to corresponding sensing electrodes (102), the feedback branch (110) is connected between the inverting end (V-) and the output end (V0), and the non-inverting end (V+) is directly or indirectly connected to the reference ground (200) to make the pressure differential between the plurality of sensing electrodes (102) and the protective layer (104) remain unchanged. In the fingerprint sensor (100), when the electrostatic discharge phenomenon occurs on the surface of the fingerprint sensor (100), the electrostatic energy can be released to the reference ground (200) through the protective layer (104), and in this way, the capability for the fingerprint sensor (100) to resist ESD can be improved. The pressure differential between the sensing electrodes (102) and the protective layer (104) remains unchanged, so that the sensitivity of the fingerprint sensor (100) is not affected.

Description

Fingerprint sensor and electronic device

The present application claims the priority of the Chinese Patent Application, filed on Jun. 13, 2016, which is hereby incorporated by reference.

Technical field

The present invention relates to the field of fingerprint recognition, and more particularly to a fingerprint sensor and an electronic device.

Background technique

In the related art, with the popularity of fingerprint sensors in smart mobile terminals, the demand for fingerprint sensors is increasing. As a human-machine interface, the fingerprint sensor needs to be in contact with the human finger and the outside world. Electrostatic discharge (ESD) directly enters the fingerprint sensor, which easily causes damage to the internal components of the fingerprint sensor.

Summary of the invention

The embodiments of the present invention aim to at least solve one of the technical problems existing in the prior art. To this end, embodiments of the present invention need to provide a fingerprint sensor and an electronic device.

A fingerprint sensor includes a plurality of sensing electrodes, a protective layer and a plurality of operational amplifiers. The protective layer is in the same layer as the plurality of sensing electrodes, the protective layer is disposed around each of the sensing electrodes, the protective layer is connected to a reference ground, wherein the reference ground is used to load the changed reference signal. Each of the operational amplifiers includes an amplifier and a feedback branch; the amplifier includes an in-phase terminal, an inverting terminal, and an output terminal, wherein the inverting terminal is coupled to a corresponding one of the sensing electrodes, and the inverting terminal and the output terminal The feedback branch is connected between the in-phase terminal directly or indirectly connected to the reference ground such that the voltage difference between the plurality of sensing electrodes and the protective layer remains unchanged.

In the above fingerprint sensor, when an electrostatic discharge phenomenon occurs on the surface of the fingerprint sensor, the energy of the static electricity can be discharged to the reference ground through the protective layer, and thus, the ability of the fingerprint sensor to resist ESD can be improved. At the same time, the voltage difference between the sensing electrode and the reference ground remains unchanged, so that the parasitic capacitance between the sensing electrode and the reference ground does not affect the acquisition of the fingerprint detection signal, thus improving the resistance At the same time as the ESD capability, this will not affect the sensitivity of the fingerprint sensor.

In some embodiments, the signal on the in-phase end is the same as the signal on the guard layer.

In some embodiments, the signal on the in-phase end is different from the signal on the guard layer, and the signal on the in-phase end remains unchanged relative to the signal on the guard layer.

In some embodiments, the signal on the in-phase end and the signal on the guard layer are both the reference signal.

In some embodiments, the reference signal is used to drive the sensing electrode to perform fingerprint sensing.

In some embodiments, the in-phase terminal is indirectly coupled to the reference ground through a signal source and receives a drive signal from the signal source that varies as a function of the signal on the reference ground.

In some embodiments, the drive signal increases as the signal on the reference ground rises and decreases as the signal on the reference ground decreases.

In some embodiments, the drive signal remains unchanged relative to the reference signal.

In some embodiments, the reference is for connecting to a device ground of an electronic device to which the fingerprint sensor is applied by a modulation circuit.

In some embodiments, the fingerprint sensor further includes the modulation circuit, the modulation circuit configured to generate the modulation signal corresponding to a voltage driving signal according to a ground signal on a device ground, and provide the modulation signal to the reference Ground.

In some embodiments, the fingerprint sensor is a self-capacitive fingerprint sensor.

In some embodiments, the fingerprint sensor further includes a signal processing circuit coupled to the output and configured to obtain fingerprint information based on the fingerprint sensing signal output by the output.

In some embodiments, the protective layer includes a plurality of guard rings connected, each guard ring disposed around each of the sensing electrodes.

An electronic device comprising the fingerprint sensor of any of the above embodiments.

In the above electronic device, when an electrostatic discharge phenomenon occurs on the surface of the fingerprint sensor, the energy of the static electricity can be discharged to the reference ground through the protective layer, and thus, the ability of the fingerprint sensor to resist ESD can be improved. At the same time, the voltage difference between the sensing electrode and the reference ground remains unchanged, so that the parasitic capacitance between the sensing electrode and the reference ground does not affect the acquisition of the fingerprint detection signal, so while improving the anti-ESD capability, Does not affect the sensitivity of the fingerprint sensor.

Additional aspects and advantages of the embodiments of the invention will be set forth in part in

DRAWINGS

The above and/or additional aspects and advantages of the embodiments of the present invention will become apparent and readily understood from

1 is a schematic structural view of an embodiment of a fingerprint sensor of the present invention.

2 is a schematic structural view of another embodiment of a fingerprint sensor of the present invention.

3 is a schematic plan view of an embodiment of an electronic device of the present invention.

detailed description

The embodiments of the present invention are described in detail below, and the examples of the embodiments are illustrated in the drawings, wherein the same or similar reference numerals indicate the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the drawings are intended to be illustrative of the invention and are not to be construed as limiting.

In the description of the present invention, it is to be understood that the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, features defining "first" or "second" may include one or more of the described features either explicitly or implicitly. In the description of the present invention, the meaning of "a plurality" is two or more unless specifically and specifically defined otherwise.

In the description of the present invention, it should be noted that the terms "installation", "connected", and "connected" are to be understood broadly, and may be fixed or detachable, for example, unless otherwise explicitly defined and defined. Connected, or integrally connected; may be mechanically connected, or may be electrically connected or may communicate with each other; may be directly connected or indirectly connected through an intermediate medium, may be internal communication of two elements or interaction of two elements relationship. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood on a case-by-case basis.

The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the invention. Furthermore, the present invention may repeat reference numerals and/or reference letters in different examples. This repetition is for simplicity and clarity. It does not itself indicate the relationship between the various embodiments and/or settings discussed. Moreover, the present invention provides examples of various specific processes and materials, but one of ordinary skill in the art will recognize the use of other processes and/or the use of other materials.

Further, the described features, structures may be combined in one or more embodiments in any suitable manner. In the following description, numerous specific details are set forth However, those skilled in the art will appreciate that the technical solution of the present invention can be practiced without one or more of the specific details or other structures, components, and the like. In other instances, well-known structures or operations are not shown or described in detail to avoid obscuring the invention.

Referring to FIG. 1 , a fingerprint sensor 100 according to an embodiment of the present invention includes a plurality of sensing electrodes 102 , a protective layer 104 , and a plurality of operational amplifiers 106 .

The protective layer 104 is in the same layer as the plurality of sensing electrodes 102, the protective layer 104 is disposed around each of the sensing electrodes 102, and the protective layer 104 is connected to the reference ground 200. Wherein, the reference ground 200 is used to load the changed reference signal.

Each operational amplifier 106 includes an amplifier 108 and a feedback branch 110. The amplifier 108 includes an in-phase terminal V+, an inverting terminal V-, and an output terminal VO, wherein the inverting terminal V- is connected to a corresponding one of the sensing electrodes 102, and The feedback branch 110 is connected between the phase terminal V- and the output terminal V0, and the non-inverting terminal V+ is directly or indirectly connected to the reference ground 200 such that the voltage difference between the plurality of sensing electrodes 102 and the protective layer 104 remains unchanged.

Therefore, in the above-described fingerprint sensor 100, when an electrostatic discharge phenomenon occurs on the surface of the fingerprint sensor 100, the energy of the static electricity can be discharged to the reference ground through the protective layer 104, and thus, the ability of the fingerprint sensor 100 to resist ESD can be improved. At the same time, the voltage difference between the sensing electrode 102 and the reference ground 200 remains unchanged, so that the parasitic capacitance between the sensing electrode 102 and the reference ground 200 does not affect the acquisition of the fingerprint detection signal, thereby improving the ESD resistance. At the same time, this does not affect the sensitivity of the fingerprint sensor 100.

Specifically, the fingerprint sensor 100 of the embodiment of the present invention is a self-capacitive fingerprint sensor.

The plurality of sensing electrodes 102 can be arranged in an array. In the embodiment, the plurality of sensing electrodes 102 are arranged in a two-dimensional array. However, in other embodiments, the plurality of sensing electrodes 102 may also be arranged in other regular or irregular manners.

A gap 112 is formed between two adjacent sensing electrodes 102. The gap 112 can be used to accommodate the protective layer 104. The sensing electrode 102 can be made of a metal material. The protective layer 104 can be made of a conductive material. The sheath 104 is insulated from the sensing electrodes 102 of the same layer.

For example, in an embodiment of the invention, the protective layer 104 is located in the gap 112 to insulate the protective layer 104 from the sensing electrode 102. In other embodiments, the gap between the protective layer 104 and the sensing electrode 102 may be filled with an insulating material to insulate the protective layer 104 from the sensing electrode 102.

In an embodiment of the invention, the signal on the in-phase terminal V+ is the same as the signal on the guard layer 104. Preferably, the signal on the in-phase terminal V+ and the signal on the guard layer 104 are reference signals. As such, the fingerprint sensing process of the fingerprint sensor 100 is simplified.

Specifically, each of the sensing electrodes 102 may correspond to a portion of the finger and form a coupling capacitance with the finger fingerprint. For example, some of the sensing electrodes 102 respectively form a plurality of first coupling capacitances with the valleys of the finger fingerprints, and some of the sensing electrodes 102 respectively form a plurality of second coupling capacitances with the ridges of the finger fingerprints. The corresponding voltage on the coupling capacitor is output through the output V0 of the amplifier 108. By detecting the voltage output from the output terminal V0, the valley information of the finger fingerprint can be distinguished, thereby implementing the fingerprint sensing function.

In the fingerprint sensing, a driving signal (for example, a pulse signal) can be input to the non-inverting terminal V+ of the amplifier 108 through the reference ground 200. Since the amplifier 108 is short, the driving signal is output to the sensing electrode 102 through the inverting terminal V-. . When the finger touches the sensing electrode 102, the coupling capacitance formed by the finger and the sensing electrode 102 changes, and the changed voltage is fed back through the feedback branch 110 and output through the output terminal V0. The voltage at the output V0 is as follows:

Where C _f is the coupling capacitance between the finger and the fingerprint sensor 100, C _fb is the feedback capacitance in the feedback branch, V _tx is the excitation voltage signal (ie, the voltage of the driving signal), and V _out is the voltage outputted by the output terminal V0 .

In an embodiment of the invention, the reference signal is used to drive the sensing electrode 102 to perform fingerprint sensing. As such, the sensing electrode 102 is driven to perform fingerprint sensing by referring to the reference signal of the ground 200, so that the principle of the fingerprint sensor 100 is simple and the cost is reduced. The reference signal can be a pulse signal.

The feedback branch 110 includes a capacitor 109 and a switch 111. The capacitor 109 and the switch 111 are both connected in parallel between the inverting terminal V- and the output terminal V0.

Specifically, the capacitor 109 can be stored by the finger and the sensing electrode 102 during fingerprint detection. The charge of the coupling capacitor is formed.

When the switch 111 is turned on, the capacitor 109 is discharged by the amplifier 108, and the charge on the capacitor 109 is zero. When the switch 111 is turned off, the capacitor 109 stores the charge of the coupling capacitor.

It should be noted that, in the embodiment of the present invention, the figure only shows four sensing electrodes 102 and one operational amplifier 106, and the four sensing electrodes 102 are arranged in an array. Accordingly, the drawings are to be regarded as illustrative only,

The protective layer 104 disposed in the same layer as the sensing electrode 102 can reduce the thickness of the fingerprint sensor 100 while ensuring the discharge of electrostatic energy, and can realize miniaturization of the electronic device to which the fingerprint sensor 100 is applied.

In some embodiments, referring to FIG. 2, the non-inverting terminal V+ is indirectly coupled to the reference ground 200 via a signal source 114 and receives a drive signal from the signal source 114 that varies as a function of the signal on the reference ground 200. Specifically, the drive signal rises as the reference signal rises and decreases as the reference signal decreases.

Specifically, in the embodiment of the present invention, the signal source 114 includes a resistor 116 and a current source 118. The resistor 116 is connected in series with the current source 118. One end of the resistor 116 is connected to the current source 118, and the other end of the resistor 116 is connected to the reference ground 200. The non-inverting terminal V+ is connected between the current source 118 and the resistor 116. Current source 118 can be connected to voltage terminal VDD.

A change in the signal on the reference ground 200 causes a change in the voltage of the resistor 116, which in turn causes the drive signal of the signal source 114 to change. The drive signal of signal source 114 is transmitted to sense electrode 202 via the inverting terminal V- of amplifier 208 to perform fingerprint sensing.

In some embodiments, the drive signal of signal source 114 remains unchanged relative to the reference signal. As such, the fingerprint sensing process of the fingerprint sensor 400 can be simplified.

In some embodiments, referring to FIG. 1, reference ground 200 is used to connect to a device ground of an electronic device to which a fingerprint sensor is applied through a modulation circuit 120.

In particular, modulation circuit 120 can be used to generate varying reference signals, such as square wave signals that produce a particular frequency change. In an example of the present invention, the modulation circuit 120 can receive the first signal and the second signal having different amplitudes, and generate the changed reference signal by alternately outputting the first signal and the second signal. The first signal can be a low level signal (such as a voltage signal of 0 volts), which can be from a device ground of the electronic device (the signal on the device ground is generally referred to as a ground signal), and the second signal can be a high level signal (eg, 3 volt voltage signal). The device ground of the electronic device can be used as a constant ground.

In this way, the generation of a varying reference signal is achieved.

In the embodiment of the present invention, the modulation circuit 120 can be applied to the fingerprint sensor 100 and the fingerprint sensor 400.

In some embodiments, the fingerprint sensor 100 further includes a signal processing circuit 122 that is coupled to the output terminal V0 and configured to obtain fingerprint information based on the fingerprint sensing signal output by the output terminal V0.

Specifically, the fingerprint sensor 100 will be described below as an example. In the embodiment of the present invention, the fingerprint sensing signal is a voltage signal outputted by the output terminal V0 of the amplifier 108. Signal processing circuit 122 includes sampling circuit 124, analog to digital converter 126, and digital signal processor 128. The sampling circuit 124 is coupled between the output terminal V0 of the amplifier 108 and the analog to digital converter 126. The sampling circuit 124 is for amplifying the voltage output from the output terminal V0 of the amplifier 108 by a set multiple.

Analog to digital converter 126 is used to convert the amplified voltage to a value and save it. Digital signal processor 128 is coupled to the output of analog to digital converter 126 to obtain the values held by analog to digital converter 126. The voltage outputted from the output terminal V0 of the digitizing amplifier 108 can conveniently obtain the voltage information corresponding to the fingerprint, thereby implementing fingerprint sensing.

It should be noted that in other embodiments, the fingerprint sensor 400 also includes the signal processing circuit described above.

In some embodiments, the protective layer 104 includes a plurality of guard rings 130 connected, each guard ring 130 disposed about each of the sensing electrodes 102.

In particular, guard ring 130 can be received in gap 112 formed between adjacent two sensing electrodes 102.

Since the protective layer 104 is located in the same layer as the plurality of sensing electrodes 102, the protective layer 104 can further ensure fingerprints in addition to the human body static electricity brought by the fingerprint sensor 100. The fingerprint sensing accuracy of the sensor 100. Compared with the protective layer 104 disposed on the upper layer or the lower layer of the sensing electrode 102, the sensing effect and the electrostatic shielding effect of the protective layer 104 and the sensing electrode 102 are relatively better.

It should be noted that the voltage signals in the

fingerprint sensor

100 or 400 are referenced to the reference signal on the reference ground 200 as a voltage reference. When fingerprint sensing is performed, the voltage signals in the

fingerprint sensor

100 or 400 both increase as the reference signal increases, and decrease as the reference signal decreases.

Referring to FIG. 3 and FIG. 1 and FIG. 2, the electronic device 300 of the embodiment of the present invention includes the fingerprint sensor 100 or the fingerprint sensor 400 of any of the above embodiments. Hereinafter, the fingerprint sensor 100 will be described as an example.

Therefore, in the electronic device 300 described above, when an electrostatic discharge phenomenon occurs on the surface of the fingerprint sensor 100, the energy of the static electricity can be discharged to the reference ground 200 through the protective layer 104, and thus, the ability of the fingerprint sensor 100 to resist ESD can be improved. At the same time, the voltage difference between the sensing electrode 102 and the reference ground 200 remains unchanged, so that the parasitic capacitance between the sensing electrode 102 and the reference ground 200 does not affect the acquisition of the fingerprint detection signal, thereby improving the ESD resistance. At the same time, this does not affect the sensitivity of the fingerprint sensor 100.

Specifically, the electronic device 300 is, for example, a portable electronic product or a home-based electronic product. Among them, portable electronic products are various types of mobile terminals, such as mobile phones, tablet computers, notebook computers, and wearable products; and home-based electronic products such as smart door locks, televisions, refrigerators, A variety of suitable electronic products such as desktop computers.

In some embodiments, the electronic device 300 includes a housing 304 in which the fingerprint sensor 100 is located. The housing 304 defines a through hole 306 that exposes the fingerprint sensor 100.

Therefore, the through hole 306 can facilitate the positioning of the finger and the fingerprint sensor 100 when the user inputs the fingerprint, which is convenient for the user to operate. In the example of the present invention, the through hole 306 is a circular through hole. It can be understood that the through hole 306 can also be a through hole of a square shape, an elliptical shape or the like. The through hole 306 may be opened at a rear surface of the housing 304.

The fingerprint sensor 100 or the fingerprint sensor 400 may also be disposed at a suitable position on the front or side of the electronic device 300. Further, the fingerprint sensor 100 or the fingerprint sensor 400 may also be disposed inside the electronic device 300 without necessarily exposing the fingerprint sensor 100 or the fingerprint sensor 400 through the through hole.

In the description of the present specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiment", "example", "specific example", or "some examples", etc. Particular features, structures, materials or features described in the embodiments or examples are included in at least one embodiment or example of the invention. In the present specification, the schematic representation of the above terms does not necessarily mean the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples.

Moreover, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, features defining "first" or "second" may include at least one of the features, either explicitly or implicitly. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless specifically defined otherwise.

Although the embodiments of the present invention have been shown and described, it is understood that the above-described embodiments are illustrative and are not to be construed as limiting the scope of the invention. The embodiments are subject to changes, modifications, substitutions and variations.

Claims

A fingerprint sensor, comprising:

Multiple sensing electrodes;

a protective layer in the same layer as the plurality of sensing electrodes, the protective layer being disposed around each of the sensing electrodes, the protective layer being connected to a reference ground, wherein the reference ground is used to load the changed reference signal;

a plurality of operational amplifiers, each of the operational amplifiers including an amplifier and a feedback branch; the amplifier includes an in-phase terminal, an inverting terminal, and an output terminal, wherein the inverting terminal is coupled to a corresponding one of the sensing electrodes, and the inverting phase The feedback branch is connected between the terminal and the output terminal, and the non-inverting terminal is directly or indirectly connected to the reference ground such that the voltage difference between the plurality of sensing electrodes and the shielding layer remains unchanged.
The fingerprint sensor according to claim 1, wherein the signal on the non-inverting end is the same as the signal on the protective layer; or the signal on the in-phase end is different from the signal on the protective layer, and the non-inverting end The signal on the signal remains unchanged relative to the signal on the guard layer.
The fingerprint sensor of claim 1 , wherein the signal on the non-inverting end and the signal on the protective layer are the reference signal, and the reference signal is used to drive the sensing electrode to perform fingerprint sensing.
A fingerprint sensor according to claim 1 wherein the in-phase terminal is indirectly connected to the reference ground via a signal source and receives a drive signal from the signal source, the drive signal being boosted by a signal on the reference ground The rise is reduced as the signal on the reference ground decreases.
The fingerprint sensor of claim 1 wherein the reference is for connection to a device location of an electronic device to which the fingerprint sensor is applied via a modulation circuit.
The fingerprint sensor according to claim 5, wherein the fingerprint sensor further comprises the modulation circuit, wherein the modulation circuit is configured to generate the modulation signal corresponding to a voltage driving signal according to a ground signal on the ground of the device, And providing the modulated signal to the reference ground.
The fingerprint sensor of claim 1 wherein the fingerprint sensor is a self-capacitive fingerprint sensor.
The fingerprint sensor of claim 1 further comprising a signal processing circuit coupled to the output and configured to obtain fingerprint information based on the fingerprint sensing signal output by the output.
A fingerprint sensor according to any of the preceding claims, wherein the protective layer comprises a plurality of guard rings connected, each guard ring being disposed around each of the sensing electrodes.
An electronic device comprising the fingerprint sensor of any of claims 1-9.